This application proposes to study the interactions of the 4.5S, 5.5S, 7S and aggregate progesterone receptors (guinea pig uterus), and to isolate the postulated non steroid binding subunits. These macromolecules will be characterized by gel filtration, ion exchange chromatography, sucrose gradient centrifugation and equilibrium dialysis. We plan to study the induction of RNA polymerase activity and the induction of mRNAs following progesterone administration. RNA polymerase activities will be studied and we shall study the effects of isolated progesterone receptors on their enzymatic activities. We feel that the mechanism of progesterone action may lie in the interactions of the subunits of the progesterone receptor with the subunits of some class of RNA polymerase. These studies should provide insight into the role of progesterone receptors in reproductive processes.